1. Field of the Invention
The present invention relates to a ceramic multi-layer circuit substrate and, more particularly, to a ceramic multi-layer circuit substrate used in a probe card and a manufacturing method thereof.
2. Description of the Related Art
A typical semiconductor test apparatus for testing electric characteristics of chips manufactured on a wafer includes a variety of constitutional parts such as a tester, a performance board, a probe card and so on. In the semiconductor test apparatus, the probe card functions to transfer a signal from the tester via the performance board to pads of the chips on the wafer and to transfer a signal from the chip pads via the performance board to the tester.
A conventional probe card is implemented with a high-temperature co-fired ceramic multi-layer circuit substrate. Specifically, a ceramic multi-layer circuit substrate is manufactured by stacking a plurality of green sheets each having via-electrodes and internal electrodes one atop the other, followed by high-temperature firing. Then, a probe card is manufactured by bonding probe pins on the ceramic multi-layer circuit substrate. In this case, however, the via-electrodes or the internal electrodes are displaced due to constriction of the ceramic green sheets during the firing.
FIG. 1 is a schematic view illustrating a surface of a conventional ceramic multi-layer circuit substrate 10 on which bonding pads are formed. Referring to FIG. 1, electrode patterns 11 are exposed through the surface layer of the ceramic multi-layer circuit substrate 10, and bonding pads 20 are formed on the electrode patterns 11, respectively. In this case, probe cards can be formed by bonding probe pins (not shown) to the bonding pads 20, respectively.
As shown in FIG. 1, the ceramic multi-layer circuit board 10 is formed of a plurality of ceramic green sheets, which are constricted in the firing thereby changing the positions of the electrode patterns 11. Then, the positions of the electrode patterns 11 do not accurately match those of the bonding pads 20. In severe cases, the electrode patterns 11 are not electrically connected with the probe pins to thereby decrease the yield of probe card products. Thus, the bonding pads 20 can be designed with a diameter 0.4 mm or more in consideration of the displacement of the electrode patterns 11 having a diameter from 0.2 to 1.2 mm, thereby causing the yield of probe cards to be about 10%. In this case, however, it is difficult to achieve high integration by decreasing the size of the bonding pads 20.
As an attempt to solve the foregoing problems, a low-temperature firing method is used to manufacture ceramic probe cards without constriction. However, even in this method, when a plurality of ceramic green sheets to be made into the ceramic probe cards has a thickness 1.5 mm or more, they would constrict in the planar direction, thereby displacing via-electrodes or internal electrodes.